HLA DR 3, DR 4 (0401, 0402, and 0405), DQ 2, and DQ 8 transgenic mice on the non-obese diabetic (NOD) background will be immunized with the three principal beta islet cell protein autoantigens: human pre pro-insulin, human glutamic acid decarboxylase 65 Kd, and human IA-2. These mice will also be homozygous for a human CD4 transgene, and for a murine MHC Class II null targeted recombinant seventeenth chromosome (Abeta 0/0). This will ensure optimal positive selection of CD 4 positive T cells on the HLA DR or DQ restricting element. T cells from immunized transgenic mice will be fused with a TCR (-) T cell hybridoma (BW 5147). Fusion products will be selected, subcloned, and screened with the immunizing protein, pools of its component peptides, and single peptides to identify the peptide specificity of each T cell hybridoma. These peptide epitopes will then be provided to the collaborating groups at the Barbara Davis Diabetes Center, the University of Washington, and the Medical College of Wisconsin, so that they can verify the existence of these T cell proliferative responses in HLA type prediabetic and recent onset type I diabetic patients. Peptide epitopes from each antigen which bind well to the DR or DQ allele under study, but do not elicit any response in transgenic mice, will also be used to test for responses in this patient population, to further verify the accuracy of peptide epitope classification in transgenic mice. The functional characteristics of each peptide epitope will be tested by characterizing the cytokine profile (IL-2, interferon gamma, TNF alpha, IL-4, IL-10) elicited in the transgenic mice and in patients' T cells by the intact protein antigen and the peptide epitopes. The combined urine and human studies should permit the design of an HLA genotype specific immunotherapy for the prevention of immunotherapy for the prevention of type I diabetes mellitus.